CHM3/W. General Certificate of Education June 2006 Advanced Subsidiary Examination. Unit 3(a) Introduction to Organic Chemistry. Time allowed: 1 hour

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1 Surname Other Names Leave blank Centre Number Candidate Number Candidate Signature General Certificate of Education June 2006 Advanced Subsidiary Examination CHEMISTRY Unit 3(a) Introduction to Organic Chemistry CHM3/W Wednesday 7 June am to 0.00 am For this paper you must have a calculator. Time allowed: hour Instructions Use blue or black ink or ball-point pen. Fill in the boxes at the top of this page. Answer all questions. Answer questions in Section A and Section B in the spaces provided. All working must be shown. Do all rough work in this book. Cross through any work you do not want marked. The Periodic Table/Data Sheet is provided on pages 3 and 4. Detach this perforated sheet at the start of the examination. Information The maximum mark for this paper is 60. The marks for questions are shown in brackets. You are expected to use a calculator where appropriate. Write your answers to the question in Section B in continuous prose, where appropriate. You will be assessed on your ability to use an appropriate form and style of writing, to organise relevant information clearly and coherently, and to use specialist vocabulary, where appropriate. For Examiner s Use Number Mark Number Mark Total (Column ) Total (Column 2) TOTAL Examiner s Initials Advice You are advised to spend about 45 minutes on Section A and about 5 minutes on Section B. CHM3/W

2 2 SECTION A Answer all questions in the spaces provided. (a) In industry, ethanol is made from ethene in an acid-catalysed reaction. Name the type of reaction. Write an equation and identify a suitable catalyst for this reaction. Type of reaction... Equation... Catalyst... (3 marks) (b) Ethanol burns completely in a plentiful supply of air, but incomplete combustion occurs if the air supply is limited. (i) Identify a solid pollutant produced by burning ethanol in a limited supply of air. (ii) Write an equation for the incomplete combustion of ethanol to produce the solid pollutant that you have identified in part (b)(i). (2 marks) 5

3 3 The Periodic Table of the Elements The atomic numbers and approximate relative atomic masses shown in the table are for use in the examination unless stated otherwise in an individual question. I II III IV V VI VII 0.0 H Hydrogen 6.9 Li Lithium Na Sodium 39. K Potassium Rb Rubidium Cs Caesium Fr Francium Be Beryllium Mg Magnesium Ca Calcium Sr Strontium Ba Barium Ra Radium Sc Scandium Y Yttrium La Lanthanum 57 * 227 Ac Actinium 89 Key relative atomic mass atomic number 47.9 Ti Titanium Zr Zirconium Hf Hafnium V Vanadium Nb Niobium Ta Tantalum Cr Chromium Mo Molybdenum W Tungsten Li Lithium 54.9 Mn Manganese Tc Technetium Re Rhenium Fe Iron Ru Ruthenium Os Osmium Co Cobalt Rh Rhodium Ir Iridium Ni Nickel Pd Palladium Pt Platinum Cu Copper Ag Silver Au Gold Zn Zinc Cd Cadmium Hg Mercury B Boron Al Aluminium Ga Gallium In Indium Tl Thallium C Carbon Si Silicon Ge Germanium Sn Tin Pb Lead N Nitrogen P Phosphorus As Arsenic Sb Antimony Bi Bismuth O Oxygen S Sulphur Se Selenium Te Tellurium Po Polonium F Fluorine Cl Chlorine Br Bromine I Iodine At Astatine He Helium 20.2 Ne Neon Ar Argon Kr Krypton Xe Xenon Rn Radon 86 * 58 7 Lanthanides Actinides 40. Ce Cerium Th Thorium Pr Praseodymium Pa Protactinium Nd Neodymium U Uranium Pm Promethium Np Neptunium Sm Samarium Pu Plutonium Eu Europium Am Americium Gd Gadolinium Cm Curium Tb Terbium Bk Berkelium Dy Dysprosium Cf Californium Ho Holmium 67 (252) Es Einsteinium Er Erbium 68 (257) Fm Fermium Tm Thulium 69 (258) Md Mendelevium Yb Ytterbium 70 (259) No Nobelium Lu Lutetium 7 (260) Lr Lawrencium 03

4 4 Gas constant R = 8.3 J K mol Table Proton n.m.r chemical shift data Type of proton δ/ppm RCH R 2 CH R 3 CH.4.6 RCOCH ROCH RCOOCH ROH Table 2 Infra-red absorption data Bond Wavenumber/cm C H C C C C C O C O O H (alcohols) O H (acids)

5 5 2 (a) Write an equation for the thermal decomposition of ethane to form ethene and one other product.... ( mark) (b) Bromoethane, CH 3 CH 2 Br, reacts with sodium hydroxide in an elimination reaction to form ethene. (i) Outline a mechanism for this elimination reaction. (ii) Suggest one reason why this method for making ethene is not used in industry. (4 marks) (c) Ethene is used to make epoxyethane. (i) State why epoxyethane is very reactive. (ii) Identify the product formed when one molecule of epoxyethane reacts with one molecule of water. Give a use for this product. Product... Use... (3 marks) 8 Turn over

6 6 3 The reaction of bromine with ethane is similar to that of chlorine with ethane. Three steps in the bromination of ethane are shown below. Step Br 2 2Br Step 2 Br + CH 3CH 3 CH 3 CH 2 + HBr Step 3 CH 3 CH 2 + Br 2 CH 3 CH 2 Br + Br (a) (i) Name this type of mechanism. (ii) Suggest an essential condition for this reaction. (iii) Steps 2 and 3 are of the same type. Name this type of step. (iv) In this mechanism, another type of step occurs in which free-radicals combine. Name this type of step. Write an equation to illustrate this step. Type of step... Equation (5 marks) (b) Further substitution in the reaction of bromine with ethane produces a mixture of liquid organic compounds. (i) Name a technique which could be used to separate the different compounds in this mixture. (ii) Write an equation for the reaction between bromine and ethane which produces hexabromoethane, C 2 Br 6, by this substitution reaction. (2 marks)

7 7 (c) The compound,2-dibromo-,,2,2-tetrafluoroethane is used in some fire extinguishers. Draw the structure of this compound. ( mark) (d) Halothane is used as an anaesthetic and has the following structure. H F Cl C C F Br F (i) Give the systematic name of halothane. (ii) Calculate the M r of halothane. (iii) Calculate the percentage by mass of fluorine in halothane. (3 marks) Turn over

8 8 4 Consider the following pairs of structural isomers. Molecular formula Structure Structure Isomer A Isomer B C 4 H 0 O H 3 C CH 3 C CH 3 CH 3 CH 2 CH 2 CH 2 OH OH Isomer C Isomer D CH 3 CH 2 C O H 3 C C CH 3 H O Isomer E CH 2 Isomer F C 6 H 2 H 2 C CH 2 H 2 C CH 2 CH 2 CH 3 CH 2 CH CHCH 2 CH 3 (a) (i) Explain what is meant by the term structural isomers. (ii) Complete the table to show the molecular formula of isomers C and D. (iii) Give the empirical formula of isomers E and F. (4 marks) (b) A simple chemical test can be used to distinguish between separate samples of isomer A and isomer B. Suggest a suitable test reagent and state what you would observe in each case. Test reagent... Observation with isomer A... Observation with isomer B... (3 marks)

9 9 (c) A simple chemical test can be used to distinguish between separate samples of isomer C and isomer D. Suggest a suitable test reagent and state what you would observe in each case. Test reagent... Observation with isomer C... Observation with isomer D... (3 marks) (d) A simple chemical test can be used to distinguish between separate samples of isomer E and isomer F. Suggest a suitable test reagent and state what you would observe in each case. Test reagent... Observation with isomer E... Observation with isomer F... (3 marks) 3 Turn over for the next question Turn over

10 0 5 There are seven isomeric carbonyl compounds with the molecular formula C 5 H 0 O The structures and names of some of these isomers are given below. Structure Name CH 3 CH 2 CH 2 CH 2 C H O pentanal CH 3 CH 3 CH 2 CH C O 2-methylbutanal H CH 3 C O 2,2-dimethylpropanal CH 3 C H CH 3 CH 3 CH 2 C O CH 2 CH 3 pentan-2-one (a) (i) Complete the table. (ii) Two other isomeric carbonyl compounds with the molecular formula C 5 H 0 O are not shown in the table. One is an aldehyde and one is a ketone. Draw the structure of each. isomeric aldehyde isomeric ketone (4 marks)

11 (b) Pentanal, CH 3 CH 2 CH 2 CH 2 CHO, can be oxidised to a carboxylic acid. (i) Write an equation for this reaction. Use [O] to represent the oxidising agent. (ii) Name the carboxylic acid formed in this reaction. (2 marks) (c) Pentanal can be formed by the oxidation of an alcohol. (i) Identify this alcohol. (ii) State the class to which this alcohol belongs. (2 marks) 8 Turn over for the next question Turn over

12 2 SECTION B Answer the question in the space provided. 6 One of the fractions obtained from petroleum can be thermally cracked to produce propene. Some of the reactions of propene are shown below. Reaction H 2 C CHCH 3 CH 3 CHBrCH 3 propene HBr Reaction 2 NH 3 CH 3 CH(NH 2 )CH 3 Reaction 3 Reaction 4 NaOH(aq) H C H CH 3 C H n CH 3 CH(OH)CH 3 substance P (a) Identify the type of reactive intermediates formed during thermal cracking and explain how they are produced. (2 marks) (b) Outline a mechanism for Reaction. (c) Outline a mechanism for Reaction 2. (4 marks) (4 marks) (d) Name substance P, which is formed in Reaction 3. Explain why substance P is a solid at room temperature. (3 marks) (e) Reaction 4 is a nucleophilic substitution reaction. Explain what is meant by the term nucleophile and identify the nucleophile in this reaction. END OF QUESTIONS (2 marks)

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16 Copyright 2006 AQA and its licensors. All rights reserved.

17 Version.0: 006 abc General Certificate of Education Chemistry 542 CHM3/W Introduction to Organic Chemistry Mark Scheme 2006 examination - June series Mark schemes are prepared by the Principal Examiner and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation meeting attended by all examiners and is the scheme which was used by them in this examination. The standardisation meeting ensures that the mark scheme covers the candidatesí responses to questions and that every examiner understands and applies it in the same correct way. As preparation for the standardisation meeting each examiner analyses a number of candidatesí scripts: alternative answers not already covered by the mark scheme are discussed at the meeting and legislated for. If, after this meeting, examiners encounter unusual answers which have not been discussed at the meeting they are required to refer these to the Principal Examiner. It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of candidatesí reactions to a particular paper. Assumptions about future mark schemes on the basis of one yearís document should be avoided; whilst the guiding principles of assessment remain constant, details will change, depending on the content of a particular examination paper. Copyright 2006 AQA and its licensors. All rights reserved

18 Chemistry, CHM3/W ñ AQA AS, Mark Scheme, June 2006 series CHM3/W SECTION A Question (a) hydration OR (electrophilic) addition (penalise incorrect words in front of the word ìadditionî e.g. ìnucleophilicî) (penalise ìindirect hydrationî but credit ìdirect hydrationî or ìsteam hydrationî) H 2 C=CH 2 + H 2 O CH 3 CH 2 OH (ignore state symbols) (credit use of C 2 H 5 OH for ethanol) (penalise use of C 2 H 6 O for ethanol on the first occasion) (credit C 2 H 4 and CH 2 =CH 2 for ethene) (penalise CH 2 CH 2, CH 2.CH 2, CH 2 :CH 2 for ethene on the first occasion) (ignore H 2 SO 4 OR extra H 2 O OR H + if it appears on both sides) conc. H 2 SO 4 OR conc. H 3 PO 4 (b) (i) Carbon OR C (credit ìsootî or ìsootyî) (penalise ìcokeî or ìcoalî) (credit ìcarbon + carbon monoxideî provided it is clear that carbon is solid; penalise ìcarbon + carbon dioxideî) (ii) CH 3 CH 2 OH + O 2 2C + 3H 2 O OR CH 3 CH 2 OH + YO 2 C + CO + 3H 2 O (credit multiples of these equations) (credit use of C 2 H 5 OH for ethanol) (penalise use of C 2 H 6 O for ethanol, but note a possible repeat error from part (a) above) Total 5 Question 2 (a) CH 3 CH 3 H 2 C=CH 2 + H 2 (credit C 2 H 6 for ethane) (credit C 2 H 4 and CH 2 =CH 2 for ethene) (penalise CH 2 CH 2, CH 2.CH 2, CH 2 :CH 2 for ethene, but check Q(a) for possible repeat error) 2

19 AQA AS, Mark Scheme, 2006 June series ñ Chemistry, CHM3/W (b) (i) M curly arrow from lone pair of electrons on oxygen of hydroxide ion (insist on a lone pair of electrons on the oxygen atom and a negative charge, but only credit this mark if the attack is to a correct H atom) M2 curly arrow from the middle of the C-H bond to the middle of the C-C bond. (only credit this mark if the arrow originates from the correct C-H bond and if an attempt has been made at M) M3 curly arrow from the middle of the C-Br bond towards/alongside the Br atom. (credit M3 independently unless the bond breaking is contradicted by an additional arrow) (penalise M3 curly arrow if the C-Br has a formal positive charge) (ignore partial charges on the C-Br bond, but penalise if incorrect) (credit full marks for an E mechanism, with M2 awarded for a correct curly arrow on the correct carbocation) (award a maximum of two marks for an incorrect haloalkane) (ignore products) (ii) (c) (i) Haloalkane/C 2 H 5 Br is made from ethene OR haloalkane is not (readily) available OR haloalkane is expensive OR it is (too) expensive/costly OR (reaction) yield is too low/poor OR it is too slow OR a valid reference to nucleophilic substitution/alcohol formation occurring as an alternative reaction. (ignore references to temperature or to energy consumption) (do not credit statements which refer to the idea that this route is not chosen, because industry chooses another route e.g. cracking) Strained ring/ bonds/ structure/molecule OR three-membered ring OR 60 o bond angle OR bond angle much less than tetrahedral (penalise ìstressed ringî) ( ignore ìweak bondsî, ignore ìunstableî) (ii) ethane-,2-diol OR correct structure (penalise ethylene glycol OR,2-dihydroxyethane if these appear alone) (credit ethan-,2-diol) (If both a structure and a formula are given, credit either correct one of these provided the other is a good, if imperfect, attempt) (used in) antifreeze OR for OR in the manufacture/making/formation of terylene, polyester, 3

20 Chemistry, CHM3/W ñ AQA AS, Mark Scheme, June 2006 series PET only (ignore reference to terylene etc. if they accompany ìantifreezeî (penalise ìde-icerî, ìsolventî, ìsurfactantî, ìplasticizerî) (If the candidate indicates that the product is antifreeze,then this can gain credit, but not if contradicted in its use e.g. as de-icer) Total 8 Question 3 (a) (i) (free-)radical substitution (both words required for the mark) (ii) uv light OR sunlight OR high temperature OR 50 o C to 500 o C (iii) Propagation (ignore ìchainî, ìfirstî, ìsecondî in front of the word propagation) (iv) Termination 0CH 2 CH 3 + Br0 CH 3 CH 2 Br OR 20CH 2 CH 3 C 4 H 0 (penalise if radical dot is obviously on CH 3, but not otherwise) (penalise C 2 H 5 -) (credit 2Br- Br 2 ) (ignore ìchainî in front of the word termination) (b) (i) Fractional distillation OR fractionation (credit gas-liquid chromatography, GLC) (ii) CH 3 CH 3 + 6Br 2 C 2 Br 6 + 6HBr (credit C 2 H 6 for ethane) (c) Correct structure for CF 2 BrCF 2 Br drawn out (penalise ìflî for fluorine) (d) (i) 2-bromo-2-chloro-,,-trifluoroethane OR -bromo--chloro-2,2,2-trifluoroethane (insist on all numbers, but do not penalise failure to use alphabet) (accept ìflourineî and ìcloroî in this instance) (ii) 97.4 only (ignore units) (iii) (57/97.4 x 00) = 28.9% OR 28.88% (credit the correct answer independently in part (d)(iii), even if (d)(ii) is blank or incorrectly calculated, but mark consequential on part (d)(ii), if part (d)(ii) is incorrectly calculated, accepting answers to 3sf or 4sf only) 4

21 AQA AS, Mark Scheme, 2006 June series ñ Chemistry, CHM3/W (penalise 29% if it appears alone, but not if it follows a correct answer) (do not insist on the % sign being given) (the percentage sign is not essential here, but penalise the use of units e.g. grams) Total Question 4 (a) (i) M (compounds with) the same molecular formula (OR this could be defined) M2 but different structural/graphical/displayed formulas OR different structures (ii) C 3 H 6 O only (iii) CH 2 only (b) potassium dichromate(vi)/k 2 Cr 2 O 7 and acid/acidified/h 2 SO 4 /HCl/H + (OR KMnO 4 /H 2 SO 4, but not HCl) (remains) orange or no change or no reaction (OR (remains) purple if KMnO 4 ) (goes or orange to) green (OR (goes or purple to) colourless if KMnO 4 in acid and accept brown ppt. or green if neutral or in alkali) (c) Potassium dichromate (VI)/K 2 Cr 2 O 7 and acid/acidified/h 2 SO 4 / H + OR (KMnO 4 /H 2 SO 4 ) Fehlingís solution OR Benedictís solution Tollensí reagent OR AgNO 3 /NH 3 OR ammoniacal siver nitrate. (penalise AgNO 3 alone, but mark on) (goes or orange to) green (goes or purple to) colourless/brown ppt./green solution if KMnO 4 used) red solid (OR yellow/green/red solid if Benedictís is used) silver mirror/coating/tube OR black/grey precipitate/solid (remains) orange or no change or no reaction (OR purple for KMnO 4 ) (remains) blue or no change or no reaction (remains) colourless or no change or no reaction 5

22 Chemistry, CHM3/W ñ AQA AS, Mark Scheme, June 2006 series (d) bromine (water) OR iodine solution OR iodine in KI (OR KMnO 4 ) Question 5 remains yellow/orange/brown/red or no change or no reaction (if KMnO 4, remains purple or no change or no reaction) (goes) colourless or decolourised (penalise ìgoes clearî and penalise ìdiscolourî) (goes or purple to) colourless/brown ppt/green solution if KMnO 4 used) In each of parts (b), (c) and (d), note the following general ideas If no reagent then CE=0 If totally wrong reagent then CE=0 If correct reagent has been attempted, whether by formula or name, but is wrongly presented, penalise the reagent, but mark on. If the candidate writes ìnothingî as the answer to a negative response, penalise this on the first occasion and then credit RE subsequently. If both observations are the same then give no credit for either, since this would fail to discriminate. Total 3 (a) (i) M pentan-3-one only M2 CH 3 CH 2 CH 2 COCH 3 (insist on C=O being drawn out) (penalise use of C 3 H 7 ) (ii) aldehyde (CH 3 ) 2 CHCH 2 CHO ketone (CH 3 ) 2 CHCOCH 3 (insist on a clear structure for the C=O of the functional groups, but do not be too harsh on the vertical bonds between carbon atomson his occasion) (If both structures correct, but wrong way around, award one mark) (ignore names) (b) (i) CH 3 CH 2 CH 2 CH 2 CHO + [O] CH 3 CH 2 CH 2 CH 2 COOH (accept C 4 H 9 CHO going to C 4 H 9 COOH) (insist on a balanced equation - for example do not credit [O] over the arrow alone) (ii) pentanoic acid (credit pentan--oic acid) (c) (i) CH 3 CH 2 CH 2 CH 2 CH 2 OH OR pentan--ol 6

23 AQA AS, Mark Scheme, 2006 June series ñ Chemistry, CHM3/W (If both a structure and a formula are given, credit either correct one of these provided the other is a good, if imperfect, attempt) (ii) Primary (credit o or ) Question 6 Total 8 (a) M (Free-)radical intermediates (credit ìalkyl radicalsî, but penalise ìcarbon radicalsî) (penalise ìradical substitutionî as a contradiction) M2 formed by breaking/splitting of C-C bonds/c-h bonds/carbon chain OR by homolysis/homolytic fission/reaction (credit M and M2 independently) (credit M2 for a correct illustration of homolysis of a C-C bond to produce radicals) (If reference to carbocations, then CE=0 for this section) (If ìheterolyticî is referred to, then penalise M2) (ignore conditions, including catalyst and temperature) Sub-total 2 marks (b) M curly arrow from C=C bond towards/alongside the side of H atom on H-Br (penalise M if arrow to formal positive charge on HBr) (ignore partial charges on H and Br of HBr, but penalise if these are incorrect) (award one mark from M+ M2 if H + is used, ignoring its formation) M2 curly arrow from H-Br bond towards/alongside the side of the Br atom. (credit the arrow even if there are partial or formal charges on H and Br) M3 correct structure of the carbocation (lose only this mark if primary carbocation is formed, then mark on) M4 curly arrow from lone pair on the bromide ion towards/alongside C atom bearing the positive charge. (insist that the bromide ion has a lone pair of electrons and a negative charge.) (award a maximum of three marks for use of the wrong alkene) Sub-total 4 marks (c) M curly arrow from lone pair on nitrogen of (correct formula for) ammonia towards/alongside C atom of C-Br (penalise M if formula of ammonia is wrong or has a negative charge or has no lone pair or arrow is not from lone pair) M2 curly arrow from C-Br bond towards/alongside side Br atom (credit M2 independently) 7

24 Chemistry, CHM3/W ñ AQA AS, Mark Scheme, June 2006 series (penalise M2 if formal positive charge on C atom of C-Br) (M2 is a possible RE from 2(b)(i)M3) M3 correct structure of the alkylammonium ion (credit the structure drawn out with all four bonds around the nitrogen atom OR written as RNH + 3 ) M4 curly arrow from the middle of one of the H-N bonds towards the (positive) N atom (N.B. it is possible to credit M4 on an alkylammonium ion which is all correct except for the omission of the positive charge) (award a maximum of three marks if the wrong haloalkane is used) (If S N mechanism is used, give full credit in which M is for a curly arrow from the lone pair of the N atom of ( correct formula for) ammonia towards/alongside the positive carbon atom of the carbocation) Sub-total 4 marks (d) M poly(propene) OR polypropene only M2 Substance P is a large molecule/macromolecule/long-chained molecule/ high M r molecule QoL (award this mark only if there is clear reference to a large molecule) M3 many intermolecular/van der Waalsí forces (of attraction) between molecules/chains OR the idea of large surface contact between molecules/chains (or wtte) (penalise M3 if reference to ìbondsî) (penalise M3 if the intermolecular forces are described as ìstrongî, but credit an answer which suggests that the overall force of attraction is strengthened/increased) (penalise M3 if the forces are described as ìdipole-dipoleî or ìhydrogen bondsî) Sub-total 3 marks (e) M electron/lone pair donor (or wtte) QoL OR a species/ molecule/ion with an electron/lone pair which can create a co-ordinate/covalent bond) (award this mark if there is clear reference to an electron pair being donated) M2 hydroxide ion (credit reference to the formula for the hydroxide ion) Sub-total 2 marks Total 5 8